Construction organization measures for corrosion prevention of pressure steel pipe in hydropower station

Construction organization measures for corrosion prevention of pressure steel pipe in hydropower station

I. Project Overview:

The contract quantity of pressure steel pipe for hydropower station is 575t, including straight pipe, elbow pipe, bifurcated pipe and branch pipe. Anti-corrosion surface area of about 6000 square meters, of which, the inner surface area of the pressure steel tube is about 2966 square meters, coated with epoxy asphalt thick paste anti-rust paint; The outer wall surface area of about 3034 square meters, coating modified cement mud.

Two, anti-corrosion construction organization measures compilation basis:

1. Code for Manufacturing, Installation and Acceptance of Pressure Steel Tubes (DL 5017-93);

2. Code for Corrosion Prevention of Hydraulic Metal Structures (SL 105-95);

3. "Technical Requirements for Anticorrosion Construction of Pressure Steel pipe of Buffujia Power Station" notice;

4. Relevant provisions of bidding contract documents;

5. Construction experience summarized in long-term construction.

Three, anti-corrosion construction technical requirements:

1, the inner surface pretreatment of the pressure steel tube should reach the Sa2 standard, and the surface roughness should reach the RY60-100 μm, the outer wall surface pretreatment should reach the Sa1 standard, and the surface roughness should reach the RY40-70 μm.

2. The inner surface of the pressure steel tube is coated with a primer paint and a top coat paint. The bottom coat is coated with "epoxy asphalt thick slurry anti-rust primer", and the coating thickness is 125μm. The top coat was "epoxy asphalt thick paste anti-rust paint top coat", the coating thickness was 175μm; After drying, the thickness of dry film is 300±10μm. The outer wall is coated with caustic soda cement slurry, the thickness is 300±10μm.

Iv. Specific measures for anti-corrosion construction:

1, in a round hole to the traffic between the hole design field, select an area of about 163 ㎡, set up two anti-corrosion 30 ㎡ workshop, a intercropping anticorrosive paint, another blast intercropping with, again laid two 25 m light rail, to produce a small car, connection sandblasting workshop and anticorrosive workshop, used in steel pipe in and out of the shop. (Please refer to the attached drawing of Steel Pipe Anti-corrosion Workshop)

2, derusting method using jet derusting construction, the equipment uses 45KW 9 square meters of air compressor, compressed air through the oil and water separation device treatment, to ensure that the compressed air is dry, no oil, and regularly clean up the oil and water separation device dirt. The local natural coarse river sand is used for sandblasting. After dusting, screening and drying, it is loaded into the sandblasting tank for sandblasting operation. The anti-corrosion operation will involve 5-6 people.

3, the welding slag, burr, oil and other pollutants on the surface of the steel pipe with steel wire brush, grinder and other tools to clean up, standing on the anti-corrosion platform, manual traction to a closed workshop, with dust-free, clean, dry sand for spray rust removal. With the air compressor wind as the power, the injection pressure is 0.5 ~ 0.7mpa, the number of injection materials is about 8 ~ 11, the Angle between the injection Angle and the normal line of the steel pipe surface is about 15 ~ 30°, and the injection distance is about 100 ~ 300mm, so as to achieve the best rust removal effect. After derusted, the inner wall of the steel pipe is up to standard Sa2 and the surface roughness is up to Ry60-100um by visual comparison with the standard photos or the test plate. The outer wall of the steel tube reaches the standard Sa1 level, and the surface roughness reaches Ry40-70um. After surface derusting treatment is completed, dry, oil-free compressed air is used to remove dust, gravel and other debris. The cleaned surface is no longer touched directly by hand, but can be operated with gloves.

4. When the steel surface temperature is below 3℃ above dew point and the relative humidity is higher than 85%, the surface derusting treatment is not carried out.

5, after the completion of rust removal process, please "three inspection" and supervision engineer acceptance, before the coating process.

6, before painting, should carefully check the variety, model, specifications of the paint used to meet the requirements of the construction technical conditions. The use of coating materials should be carried out in accordance with "Technical Requirements for Anticorrosive Construction of Pressure Steel Pipe of Buffalo Hydropower Station" and the manufacturer's instructions.

7. Before anticorrosion, make the coating process test in advance in accordance with the "Code for Anticorrosion of Hydraulic Metal Structure" (SL 105-95) and "Technical Requirements for Anticorrosion Construction of Pressure Steel Pipe of Shuihujia Power Station", and submit it to the supervision engineer for approval.

8. The inner wall coating material of the steel pipe is "epoxy asphalt thick slurry anti-rust paint", which is divided into two layers. The first layer is "epoxy asphalt thick slurry anti-rust primer" with the coating thickness of 125μm, and the second layer is "epoxy asphalt thick slurry anti-rust top paint" with the coating thickness of 175μm. Before blending the coating, read the coating instructions carefully, master the blending method of "epoxy asphalt thick slurry anti-rust paint", mix it with the mixture ratio of 1:10 by weight and stir evenly, and use it after half an hour of aging. If the paint or particles are found, it should be filtered by 80-110 mesh screen before coating. Under the normal temperature of 25℃, the good coating should be used up within 6 hours, otherwise, for the application fee treatment.

9, rust qualified surface in 4 hours, using the method of roll coating and brush coating. In sunny days and under normal atmospheric conditions, the maximum coating time should not exceed 11h. After the primer is applied, wait for the surface to dry for more than 24h before applying the next layer of paint.

10. In order to prevent layer rise or fall off, in the case of low ambient temperature, the electric furnace is used for appropriate heating in the closed workshop to ensure that the ambient temperature and humidity meet the requirements.

11. In the process of coating, the thickness of wet film should be often measured. Defects such as leakage, flow and wrinkling should be dealt with in time if found during coating. Before the film is dry, in case of rain, rain prevention measures should be made to avoid contamination by the rain. Staff are strictly prohibited to tread on the paint film.

12. When the relative humidity in the air exceeds 85%, the steel surface temperature is below 3℃ above the atmospheric dew point and the adverse environment specified in the manual, the coating shall not be carried out.

13. The coated steel pipe shall be protected from damage and harmful effects caused by high temperature, scorching heat and adverse climatic conditions during the hoisting process. In the process of transportation and installation caused by the film fall off, according to the pretreatment, painting, quality inspection procedures, the implementation of the patch.

14. Within the range of 100mm on both sides of the ring joint, after surface pretreatment, apply workshop primer that does not affect the weldability. After welding the circular joint, the secondary derusting is carried out, and then the manual rolling or brushing is used.

15. After derusted, the outer wall of the pipe is evenly coated with a layer of caustic soda cement slurry, and attention is paid to maintenance after coating.

16, anti-corrosion construction period: July 20th - October 30th.

V. Quality inspection:

1. Check the quality of the surface pretreatment before coating, and the coating can be carried out after passing the standard.

2. In the process of coating, wet film thickness meter is often used to measure the wet film thickness in time.

3, each layer of coating, should be the previous layer of appearance inspection, such as leakage of coating, flow hanging, crepe and other defects, should be handled in time. After finishing the coating, the appearance of the coating film is checked. The surface is uniform and consistent, without defects such as flow hanging, crepe, bulge, pinhole, crack and so on. Cement slurry coating thickness should be basically consistent, adhere firmly, can not afford powder.

4, the film curing and drying, dry film thickness determination, 85% to the thickness of the measuring point should reach the required thickness, did not reach the thickness of the measuring point, the minimum thickness should not be less than 85% of the required thickness, that is, 255μm.

5, measurement method: measurement, each measuring point should take three readings, each reading of the location of 25-75 mm, take the arithmetic mean of three readings, the measured value of this point. Take 3 measuring points on the surface of each pipe joint.

6. Inspection of adhesion and separation resistance between layers: draw two intersecting lines with an Angle of 60 degrees on the coating, draw deep enough to see the base steel pipe, stick the slit part with tape, and then tear the tape quickly along the vertical direction, and the coating should not peel off. (The non-important parts of the steel pipe should be selected for this inspection, and the coating should be made up immediately after the test)

7, with the pinhole detector to comprehensively check the surface for pinholes, pinholes found, immediately after polishing.

Vi. Quality Assurance Measures:

1. Execution standard of anti-corrosion construction: Code for Manufacturing, Installation and Acceptance of Pressure Steel Tube (DL 5017-93); Code for corrosion Prevention of Hydraulic metal Structures (SL 105-95);

2. The construction quality shall comply with the provisions of relevant regulations, specifications and technical provisions.

3. Establish and perfect anti-corrosion coating inspection records, and set up full-time quality inspectors to track and inspect each process.

4, anti-corrosion process, strict implementation of the "process quality transfer card" system, unqualified products are never allowed to be transferred to the next process. The quality responsible person for each process must sign the process quality transfer card to confirm that the process quality has met the specification requirements. The next process may refuse to accept the product that does not meet the requirements of the specification. Each process according to the requirements of product quality self - check, and truthfully fill in the quality record form. Through the dynamic "process quality transfer card" and the static quality record form, the whole construction process is implemented the total quality management, to ensure that the steel pipe anti-corrosion quality reaches the excellent standard. During the construction process, strengthen the connection of the construction process, and check each process according to the "triple inspection system" procedure.

4. Timely collect and sort out the original construction records, data, instructions, reorganizing statements and completion data, analyze the dynamic information of construction quality and work quality, formulate measures to improve construction quality and improve the quality management level.

5. Improve the quality awareness of anticorrosive personnel, firmly establish the view of quality first, popularize the total quality management education of staff, strengthen technical training, adhere to the first training after the post, and promote the continuous improvement of construction quality level.

6, anti-corrosion coating paint, dilution economy and other main materials, must have the factory certificate, its technical parameters meet the technical requirements, unqualified materials are not allowed to use.

7, anti-corrosion construction, strictly according to the process measures, and in the construction process of strict monitoring.

8, strict quality control, in the process of anti-corrosion construction, the occurrence of quality defects or accidents, adhere to the "three not let go" principle, in-depth on-site serious analysis and serious treatment.

9, anti-corrosion construction quality must be strict rewards and punishments, and implement the principle of quality and economy, to make contributions to the quality of anti-corrosion construction to reward, to the quality of the loss of people to be punished.

10. After the coating is finished, the quality inspector shall conduct a comprehensive quality inspection and acceptance of the coating surface of the steel pipe together with the supervision engineer, and submit the quality inspection results of the steel pipe coating to the supervision engineer for signature and confirmation.

Vii. Safety guarantee Measures:

1, in the anti-corrosion construction must adhere to the "safety first, prevention first" policy, earnestly implement the "safety in production, everyone is responsible for" principle, adhere to the implementation of national safety in production laws, regulations and policies.

2. Anticorrosive construction personnel should conscientiously perform their duties of safe construction. The working area is equipped with full-time safety officers, and the shift group is equipped with part-time safety inspectors, who are responsible for the safety inspection work in the construction, and often check the good condition of the anti-corrosion work place, construction machinery and instruments in the anti-corrosion shift. The anticorrosion team will organize the safety day activity once a week and make a good record. Insist on five minutes of safety education before work every day.

3, anti-corrosion work is toxic work, work should be done to prevent gas protection, wear a mask, wear dust-proof clothes, pay special attention to fire prevention, ventilation and protect the health of workers. On the wall height, should also fasten the safety belt.

4, in the spray operation, pay attention to prevent spray wounding, at the same time, pay attention to mechanical equipment wounding hands and feet.

5, paint, dilution and other chemical materials, dangerous goods in the process of transportation, storage and use, formulate the corresponding regulations, and strict implementation, to prevent accidents.

6, equipped with fire-fighting facilities and equipment, temporary shed safety needs to meet the fire regulations, and equipped with enough fire-fighting equipment to prevent the occurrence of fire accidents.

7. The ventilation condition of the anti-corrosion working environment of steel pipe should be good to reduce the harm of dust pollution to human body.

Viii. Environmental Protection Measures:

1. In order to solve the problem of rust removal dust in the process of corrosion prevention of pressure steel pipe, the anticorrosion workshop is built in a remote place outside the traffic hole, and two closed workshops are built to prevent the dust when rust removal from floating with the wind and polluting the surrounding environmental hygiene.

2. The coating operation is carried out in a closed workshop, and the rolling coating and brush coating construction technology can be fully achieved